季节性冻融期浅层潜水与土壤水转化规律的试验研究

During seasonal freezing and thawing period, soil moisture experienced several freeze-thaw cycles and the soil moisture-heat coupled migrated more complex, that intensified the transformation between shallow phreatic water and soil water greatly, which not only change the quantity of groundwater resources, but also aggravate the soil salinization. Based on the monitoring of phreatic water evaporation and infiltration, soil moisture, soil temperature and soil water potential of field lysimeter through two natural freeze-thaw period, and supplemented by one-way soil freezing test under man-controlled freezing temperature, the law of soil moisture-heat migration, phreatic water evaporation and the transformation between phreatic water and soil water during freezing and thawing period in homogeneous and heterogeneous soil with different groundwater level depth will be analyzed in this study. This research will reveal the influence of freezing temperatures changes, the soil heterogeneity, soil particle size distribution and average particle diameter, the thickness and position of frozen layer and groundwater level depth on the transformation between phreatic water and soil water. Then, it will explore the forecasting model of transformation amount between phreatic water and soil water during seasonal freezing and thawing period. The research results not only provide theoretical basis for the scientific evaluation of groundwater resources quantity and reasonable revealing mechanism of soil moisture evaporation during freezing and thawing period, but also make great significance for high efficient utilization of soil water resources and prevention of soil salinization.

季节性冻融期，土壤水分经历多次冻融循环作用并发生复杂的水、热耦合迁移，加剧浅层潜水与土壤水之间的水分迁移转化，不仅使地下水资源量发生变化，而且易加重土壤盐渍化等水土环境问题。本研究通过2个自然冻融期地中蒸渗仪系统潜水蒸发量与入渗补给量、土壤含水率、土壤温度及土水势的监测，辅以室内人为控制冻结气温不同潜水位埋深下的土壤单向冻结试验，分析研究冻融期潜水浅埋条件下均质和非均质土壤水热迁移，潜水蒸发、潜水与土壤水相互转化的规律；揭示冻结气温变化、土壤的非均质性、土壤颗粒级配及平均粒径、冻层厚度及层位、潜水位埋深等对冻融期潜水与土壤水相互转化量的影响；探索季节性冻融期浅层潜水与土壤水转化量的预报模型。研究成果不仅可为科学评价地下水资源量及合理揭示冻融土壤水分蒸发机理提供理论依据，而且对于土壤水资源的高效利用、土壤盐渍化的防治具有重要意义。

在地下水浅埋区，潜水与土壤水相互转化十分强烈，特别是在季节性冻融期，土壤冻结与融化作用使得转化过程更加复杂。浅层潜水与土壤水之间的水分迁移转化，不仅使地下水资源量发生变化，而且易导致土壤盐渍化等水土环境问题。本研究利用地中蒸渗仪系统，通过2个自然冻融期潜水蒸发量与入渗补给量、土壤含水率、土壤温度及土水势的监测，辅以室内人为控制冻结气温不同潜水位埋深下的土壤单向冻结试验，分析研究了冻融期潜水浅埋条件下非饱和带土壤水分迁移特征及潜水蒸发、潜水与土壤水相互转化的规律；建立了冻结期累积潜水蒸发量与冻结时间的关系以及冻融期潜水补耗差与地下水位埋深及土壤平均粒径的预报模型；揭示了地下水位埋深和土壤质地对土壤冻融过程中水分迁移、潜水蒸发以及潜水补耗差的影响。主要结论：冻融期，不同地下水位埋深下的非饱和带土壤含水率差异较大，地下水位埋深越浅，水分聚集区形成越早，土壤含水量越高。当地下水位埋深为1.0m时，剖面含水率增加幅度最大，砂壤土剖面水分主要在40-70cm处聚集，土壤含水率达到51%。潜水与土壤水之间的转化受非饱和带岩性、地下水位埋深和土壤冻融过程的影响，地下水位埋深越小，土壤颗粒越小，冻融期土壤剖面水分冻结引起的潜水入流量越大。冻结期，累积潜水入流量与冻结历时具有较好的相关性，二者符合幂指数关系。冻融期平均潜水补耗差与地下水位埋深满足半对数关系，模型的回归系数与土壤平均粒径呈线性关系。研究成果不仅可为科学评价地下水资源量提供理论依据，而且对于土壤盐渍化的防治具有重要意义。